Hydraulics Used in many applications in industry!

Hydraulics An area of engineering science that deals with liquid flow and pressure Use syringes to demonstrate the basic concept of hydraulic flow

Hydraulic Fluids Liquid pumped through a hydraulic system Petroleum-based or synthetic oil Serve four major functions: 1. Power transmission 2. Lubrication of moving parts 3. Sealing of spaces between moving parts 4. Heat removal Relatively Incompressible! Four major functions: Power transmission: Pumps apply pressure to hydraulic fluids, which causes the fluid to move (since they can’t be compressed). This movement causes components connected to the hydraulic system to move. Thus, power is transmitted. Lubrication of moving parts: Hydraulic systems provide their own lubrication! Sealing of spaces between moving parts: Hydraulic pressure between moving parts (e.g. piston) makes a seal between those parts. Heat removal: Hydraulic fluids move passed hot components and then carry that heat away via conduction mechanisms.

Two Types or Conditions of Hydraulic Systems Hydrostatic Hydrodynamic Four major functions: Power transmission: Pumps apply pressure to hydraulic fluids, which causes the fluid to move (since they can’t be compressed). This movement causes components connected to the hydraulic system to move. Thus, power is transmitted. Lubrication of moving parts: Hydraulic systems provide their own lubrication! Sealing of spaces between moving parts: Hydraulic pressure between moving parts (e.g. piston) makes a seal between those parts. Heat removal: Hydraulic fluids move passed hot components and then carry that heat away via conduction mechanisms.

Hydrostatics - a “No Flow” Scenario “Static” means “stationary” or “non flowing” in a hydraulic system Hydraulic systems are considered static when there is no flow Pascal’s Law (for hydrostatics): a pressure applied to a confined hydrostatic fluid is transmitted with equal intensity throughout the fluid Same pressure throughout!

Hydrodynamics – a “Flow” scenario “Dynamic” means “moving” or “flowing” in a hydraulic system Hydraulic systems are considered dynamic when there is flow Pascal’s Law does not apply! Pressure does not have equal intensity in a flowing dynamic system Pressure drops along the length of a hydraulic line in flowing systems

Flow and Pressure Flow, Q Pressure, P volume flow rate amount of fluid moving through system per unit time Pressure, P force per unit area of fluid moving through a system

Mechanical Advantage Ideal Mechanical Advantage (IMA) Assumes no frictional losses Calculated as ratio of output force to input force

Ideal Mechanical Advantage

Mechanical Advantage Actual mechanical advantage (AMA) always less than ideal difficult to calculate

Application of Pascal’s Law in a Simple Hydrostatic System In the schematic on the following slide: How much force must you exert on piston A to lift a load on piston B of 500 lbs?

What is the ideal mechanical advantage of this system?

Problem Solving - Step 1 Known Unknown A = 500 in2 P=? F = 500 lb Determine the pressure in the system using information about piston B Known Unknown A = 500 in2 P=? F = 500 lb Equation No algebra needed Substitution & Solution

Step 2 Pressure units Known Unknown A = 1.0 in2 F=? Use the pressure calculated in STEP 1 and information about piston A to calculate force: Known Unknown A = 1.0 in2 F=?

Step 2 = Algebraic solutions

Step 3 - Determine the IMA Using information from STEPS 1 & 2 Known Unknown F(input) = 1 lb IMA=? F(output) = 500 lb Equation No algebra needed

Step 4 - Substitution & Solution

A Hydraulic System

Tank/Reservoir Storage device which is open and not pressurized Filter

Pumps Centrifugal pump (Vane Pump): no specific amount of fluid flow per rotation; flow depends on speed of blades Positive displacement pump (Gear Pump): a specific amount of fluid passes through the pump for each rotation

Accumulators Storage device which is closed and is under pressure

Valves Check Valve Directional Control

Use hydraulic power to move linearly Linear Actuators Use hydraulic power to move linearly Single Acting Double Acting

Rotary Actuators Use hydraulic power to rotate Single-Vane Double-Vane

Applications Robotics Oil systems in vehicles (e.g. brakes) Presses Heavy equipment Wood splitter Aircraft control systems

In-line Pressure Gauge Directional Control Valve The Hydraulic Trainer In-line Pressure Gauge Supply line Connections Return line Connections Pressure Regulator Return line from reservoir Flow Control Valve Pressure line Check Valve Pump Actuators Motor Inline-Tee Directional Control Valve